TEACHER RESOURCE SCIENCE CONTENT/ CURRICULUM LINK PLANET EARTH AND BEYOND – OBSERVING STARS AND STARDOME OBSERVATORY & PLANETARIUM INVESTIGATING FACTS, RESOURCES AND ACTIVITIES ON... IN SCIENCE star twinkling Except for the Sun, stars are too distant to see their round shape. Even astronauts orbiting Earth see Light from a star stars that are just points of light without any edges. Astronauts observe perfectly steady points, unaffected by Earth’s atmosphere. However, we see stars that twinkle to various degrees, producing the dancing, romantic, mysterious faint lights of the nursery song we all know. Atmosphere has ‘Twinkling’ is an effect called scintillation, which is moving pockets of the distortion of starlight by changing air masses. cold and warm air Layers of warmer and cooler air have different densities, which refract (bend) light at different angles. Further scintillation is enhanced by the turbulence of moving and changing air masses. The higher a star is in the sky, the less atmosphere you are looking through. As you observe stars at *not to scale lower altitudes, eventually reaching the horizon, the starlight is traversing Adaptive optics uses increasingly longer paths of celestial images. While there is a technical an artificial star through the atmosphere. procedure for recording the seeing at a location created with lasers. at any particular time, amateur observers often ~~~ The starlight is increasingly use the Pickering Scale. This ranges from ‘1’, where Twinkling is similar distorted, producing more the image is dancing wildly and there is no central to shimmering twinkling, and becoming star point, to ‘10’, where there is a clear completely images above hot dimmer (an effect called roofs and roads on ‘extinction’). stationary point. hot summer days. Star images are also badly The Antoniadi Scale is also used, which ranges from affected by the different ‘I’ (perfect image without quivering) to ‘V’ (hardly air temperatures near an able to draw a rough sketch). observatory, especially at sunset. The dome or To help overcome these difficulties, many telescope room needs to be opened up at dusk observatories are built on mountain peaks, which to dissipate the heat of the day. Depending on the are above much of the cloud cover and moisture surrounding landscape and other nearby buildings, in the atmosphere. it can take several hours for convection currents Astronomers have also developed the technology to subside and the air to settle. of ‘adaptive optics’, which adjusts the shape of All these effects combined affect ‘astronomical telescope mirrors in real time, compensating for seeing’, which is a measure of the degree of blurring the distortions caused by the atmosphere. Check out these other resources... en.wikipedia.org/wiki/Astronomical_seeing The Pickering astronomical seeing scale: damianpeach.com/pickering.htm Is cloud cover more or less at Where in New Zealand night-time compared with daytime? is cloud cover lowest during the year? DISCUSSION POINTS STARDOME.ORG.NZ 09 624 1246 ACTIVITY STARDOME OBSERVATORY & PLANETARIUM star twinkling ACTIVITY TWO ACTIVITY ONE NIGHT-TIME OBSERVING CLASS ACTIVITY: WAVE FRONTS Encourage students to look up at night to further their understanding on ‘twinkling’ stars In groups, children will use ropes and themselves to investigate the nature of Compare the twinkling of stars on nights that light in these interactive activities. are clear and still with nights that are breezy or stormy. Try to observe the same stars in Follow this article from NASA’s different conditions for a direct comparison. Spaceplace for further instructions. Your students will investigate: Compare the effects on the twinkling of a Wave fronts – the wave nature of star from observing unaided, with binoculars, light in space telescopes with increasingly larger lenses or mirrors, and with increasing magnification. Turbulence – the disturbance of light waves in the atmosphere • Does increasing the magnification overcome twinkling? Mirroring – the reflection of waves • Try using large binoculars (15×, 25×, 30×) on Adaptive optics how mirrors can fix a tripod distorted wave fronts • Is there a difference using telescopes with spaceplace.nasa.gov/review/classroom- lenses or mirrors? activities/pdf/adaptive_optics.pdf ATMOSPHERIC TURBULENCE ACTUATORS LIGHT FROM STAR TELESCOPE MIRRORS TEACHER take a photo of your activity and send it to us. we'd love to see it! [email protected] STARDOME.ORG.NZ 09 624 1246.